class OrderedSet(object):
"""
An implementation of OrderedSet based on the keys of
an OrderedDict.
"""
def __init__(self, iterable=None):
self.data = OrderedDict()
if iterable is not None:
self.update(iterable)
def update(self, container):
check_deterministic(container)
for elem in container:
self.add(elem)
def add(self, key):
self.data[key] = None
def __len__(self):
return len(self.data)
def __contains__(self, key):
return key in self.data
def discard(self, key):
if key in self.data:
del self.data[key]
def remove(self, key):
if key in self.data:
del self.data[key]
else:
raise KeyError(key)
def __iter__(self):
return self.data.__iter__()
def __reversed__(self):
return self.data.__reversed__()
def pop(self, last=True):
raise NotImplementedError()
def __eq__(self, other):
# Note that we implement only the comparison to another
# `OrderedSet`, and not to a regular `set`, because otherwise we
# could have a non-symmetric equality relation like:
# my_ordered_set == my_set and my_set != my_ordered_set
if isinstance(other, OrderedSet):
return len(self) == len(other) and list(self) == list(other)
elif isinstance(other, set):
# Raise exception to avoid confusion.
raise TypeError(
'Cannot compare an `OrderedSet` to a `set` because '
'this comparison cannot be made symmetric: please '
'manually cast your `OrderedSet` into `set` before '
'performing this comparison.')
else:
return NotImplemented
